Technical Field
The present invention relates to a method of exfoliating a microcrystal by short pulses of UV-light irradiation.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Photomechanical materials can be used to directly transform light to mechanical work. See Kim, T. et al. Chemphyschem 2014, 15, 400-14; Zhu, L. et al. “Photomechanical Effects in Photochromic Crystals.” In Photomechanical Materials, Composites, and Systems; John Wiley & Sons, Ltd: Chichester, UK, 2017; pp. 233-274—each incorporated herein by reference in its entirety. While polymer-based materials that incorporate photochromic molecules have received much attention, recent work has demonstrated that molecular crystals composed solely of photochromic molecules can also deform under light exposure. See Min Lee, K.; Lynch, B. M.; Luchette, P.; White, T. J. Photomechanical effects in liquid crystal polymer networks prepared with m-fluoroazobenzene. J. Polym. Sci. Part A Polym. Chem. 2014, 52, 876-882, doi:10.1002/pola.27072; Eisenbach, C. D. ISOMERIZATION OF AROMATIC AZO CHROMOPHORES IN POLY(ETHYL ACRYLATE) NETWORKS AND PHOTOMECHANICAL EFFECT. Polymer 1980, 21, 1175-1179, doi:10.1016/0032-3861(80)90083-X; Ikeda, T.; Mamiya, J. I.; Yu, Y. Photomechanics of liquid-crystalline elastomers and other polymers. Angew. Chemie—Int. Ed. 2007, 46, 506-528, doi:10.1002/anie.200602372; and Matějka, L.; Ilavský, M.; Dušek, K.; Wichterle, O. Photomechanical effects in crosslinked photochromic polymers. Polymer 1981, 22, 1511-1515, doi:10.1016/0032-3861(81)90321-9, each incorporated herein by reference in their entirety. Such photomechanical molecular crystals can execute a variety of motions including bending, twisting, coiling, rolling, expanding, sliding of layers, and jumping. See Al-Kaysi, R. O.; Bardeen, C. J. Reversible Photoinduced Shape Changes of Crystalline Organic Nanorods. Adv. Mater. 2007, 19, 1276-1280, doi:10.1002/adma.200602741; Zhu, L.; Al-Kaysi, R. O.; Bardeen, C. J. Reversible photoinduced twisting of molecular crystal microribbons. J. Am. Chem. Soc. 2011, 133, 12569-12575, doi:10.1021/ja201925; Kim, T.; Al-Muhanna, M. K.; Al-Suwaidan, S. D.; Al-Kaysi, R. O.; Bardeen, C. J. Photoinduced Curling of Organic Molecular Crystal Nanowires. Angew. Chemie Int. Ed. 2013, 52, 6889-6893, doi:10.1002/anie.201302323; Al-Kaysi, R. O.; Müller, A. M.; Bardeen, C. J. Photochemically Driven Shape Changes of Crystalline Organic Nanorods. J. Am. Chem. Soc. 2006, 128, 15938-15939, doi:10.1021/ja064535p; Zhang, Y.; Peng, C.; Cui, B.; Wang, Z.; Pang, X.; Ma, R.; Liu, F.; Che, Y.; Zhao, J. Direction-Controlled Light-Driven Movement of Microribbons. Adv. Mater. 2016, 1-8, doi:10.1002/adma.201602411; Naumov, P.; Sahoo, S. C.; Zakharov, B. A.; Boldyreva, E. V. Dynamic single crystals: Kinematic analysis of photoinduced crystal jumping (the photosalient effect). Angew. Chemie—Int. Ed. 2013, 52, 9990-9995, doi:10.1002/anie.201303757; Medishetty, R.; Husain, A.; Bai, Z.; Runčevski, T.; Dinnebier, R. E.; Naumov, P.; Vittal, J. J. Single Crystals Popping Under UV Light: A Photosalient Effect Triggered by a [2+2] Cycloaddition Reaction. Angew. Chemie Int. Ed. 2014, 53, 5907-5911, doi:10.1002/anie.201402040; and Sahoo, S. C.; Sinha, S. B.; Kiran, M. S. R. N.; Ramamurty, U.; Dericioglu, A. F.; Reddy, C. M.; Naumov, P. Kinematic and mechanical profile of the self-actuation of thermosalient crystal twins of 1,2,4,5-tetrabromobenzene: A molecular crystalline analogue of a bimetallic strip. J. Am. Chem. Soc. 2013, 135, 13843-13850, doi:10.1021/ja4056323, each incorporated herein by reference in their entirety. There is considerable evidence that the crystal size and shape can have a profound effect on its photoinduced mechanical response. For example, in many cases the photomechanical crystal dimensions must be on the order of microns or less to avoid fracture or disintegration upon responding to light stimulus. In larger crystals, the build-up of internal strain due to the simultaneous presence of both reactant and product domains can lead to fracture and loss of crystal integrity. Naumov and coworkers have shown that sudden release of kinetic energy during the fracture process can propel microcrystal fragments over large distances (the photosalient phenomenon), but this process is difficult to control with fragments flying in all directions. Even for microcrystals composed of the same molecule and packing motif, different shapes can lead to different modes of mechanical motion, ranging from bending to twisting to shattering. See Kim, T.; Al-Muhanna, M. K.; Al-Suwaidan, S. D.; Al-Kaysi, R. O.; Bardeen, C. J. Photoinduced Curling of Organic Molecular Crystal Nanowires. Angew. Chemie Int. Ed. 2013, 52, 6889-6893, doi:10.1002/anie.201302323—incorporated herein by reference in its entirety. In order to generate photoactive molecular crystals with well-defined mechanical responses, as well as identify new modes of action, it is necessary to develop methods to control crystal shape and dimensions in a reproducible manner. As an example of a new photomechanical response, if a crystal could split apart in a controlled, reproducible way, the “problem” of photoinduced fracture might become a feature that could instead be harnessed.
The use of co-precipitation of organic molecules from aqueous surfactants has proven to be a general way to prepare uniform size nano- and microcrystal suspensions of organic crystals. See Kim, T.; Zhu, L.; Al-Kaysi, R. O.; Bardeen, C. J. Organic photomechanical materials. Chemphyschem 2014, 15, 400-14, doi:10.1002/cphc.201300906; Zhu, L.; Tong, F.; Al-Kaysi, R. O.; Bardeen, C. J. Photomechanical Effects in Photochromic Crystals. In Photomechanical Materials, Composites, and Systems; John Wiley & Sons, Ltd: Chichester, UK, 2017; pp. 233-274 ISBN 9781119123279; Min Lee, K.; Lynch, B. M.; Luchette, P.; White, T. J. Photomechanical effects in liquid crystal polymer networks prepared with m-fluoroazobenzene. J. Polym. Sci. Part A Polym. Chem. 2014, 52, 876-882, doi:10.1002/pola.27072; Eisenbach, C. D. ISOMERIZATION OF AROMATIC AZO CHROMOPHORES IN POLY(ETHYL ACRYLATE) NETWORKS AND PHOTOMECHANICAL EFFECT. Polymer (Guildf). 1980, 21, 1175-1179, doi:10.1016/0032-3861(80)90083-X; Ikeda, T.; Mamiya, J. I.; Yu, Y. Photomechanics of liquid-crystalline elastomers and other polymers. Angew. Chemie—Int. Ed. 2007, 46, 506-528, doi:10.1002/anie.200602372; Matějka, L.; Ilavský, M.; Dušek, K.; Wichterle, O. Photomechanical effects in crosslinked photochromic polymers. Polymer (Guildf). 1981, 22, 1511-1515, doi:10.1016/0032-3861(81)90321-9; Al-Kaysi, R. O.; Bardeen, C. J. Reversible Photoinduced Shape Changes of Crystalline Organic Nanorods. Adv. Mater. 2007, 19, 1276-1280, doi:10.1002/adma.200602741; Zhu, L.; Al-Kaysi, R. O.; Bardeen, C. J. Reversible photoinduced twisting of molecular crystal microribbons. J. Am. Chem. Soc. 2011, 133, 12569-12575, doi:10.1021/ja201925p; Kim, T.; Al-Muhanna, M. K.; Al-Suwaidan, S. D.; Al-Kaysi, R. O.; Bardeen, C. J. Photoinduced Curling of Organic Molecular Crystal Nanowires. Angew. Chemie Int. Ed. 2013, 52, 6889-6893, doi:10.1002/anie.201302323; Al-Kaysi, R. O.; Miller, A. M.; Bardeen, C. J. Photochemically Driven Shape Changes of Crystalline Organic Nanorods. J. Am. Chem. Soc. 2006, 128, 15938-15939, doi:10.1021/ja064535p; Zhang, Y.; Peng, C.; Cui, B.; Wang, Z.; Pang, X.; Ma, R.; Liu, F.; Che, Y.; Zhao, J. Direction-Controlled Light-Driven Movement of Microribbons. Adv. Mater. 2016, 1-8, doi:10.1002/adma.201602411; Naumov, P.; Sahoo, S. C.; Zakharov, B. A.; Boldyreva, E. V. Dynamic single crystals: Kinematic analysis of photoinduced crystal jumping (the photosalient effect). Angew. Chemie—Int. Ed. 2013, 52, 9990-9995, doi:10.1002/anie.201303757; Medishetty, R.; Husain, A.; Bai, Z.; Runčevski, T.; Dinnebier, R. E.; Naumov, P.; Vittal, J. J. Single Crystals Popping Under UV Light: A Photosalient Effect Triggered by a [2+2] Cycloaddition Reaction. Angew. Chemie Int. Ed. 2014, 53, 5907-5911, doi:10.1002/anie.201402040; Sahoo, S. C.; Sinha, S. B.; Kiran, M. S. R. N.; Ramamurty, U.; Dericioglu, A. F.; Reddy, C. M.; Naumov, P. Kinematic and mechanical profile of the self-actuation of thermosalient crystal twins of 1,2,4,5-tetrabromobenzene: A molecular crystalline analogue of a bimetallic strip. J. Am. Chem. Soc. 2013, 135, 13843-13850, doi:10.1021/ja4056323; Zhang, X.; Zhang, X.; Zou, K.; Lee, C.-S.; Lee, S.-T. Single-crystal nanoribbons, nanotubes, and nanowires from intramolecular charge-transfer organic molecules. J. Am. Chem. Soc. 2007, 129, 3527-32, doi:10.1021/ja0642109; Lu, L. T.; Tung, L. D.; Robinson, I.; Ung, D.; Tan, B.; Long, J.; Cooper, A. I.; Femig, D. G.; Thanh, N. T. K. Size and shape control for water-soluble magnetic cobalt nanoparticles using polymer ligands. J. Mater. Chem. 2008, 18, 2453; Bakshi, M. S.; Sachar, S.; Kaur, G.; Bhandari, P.; Kaur, G.; Biesinger, M. C.; Possmayer, F.; Petersen, N. O. Dependence of crystal growth of gold nanoparticles on the capping behavior of surfactant at ambient conditions. Cryst. Growth Des. 2008, 8, 1713-1719, doi:10.1021/cg8000043; Xiao, J.; Qi, L. 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ACS Nano 2012, 6, 5309-5319, doi:10.1021/nn3011398, each incorporated herein by reference in their entirety. Several groups have shown that varying parameters like concentration, temperature, and nature of surfactant can lead to the growth of crystals with different shapes and faceting. In the present disclosure, a divinyl anthracene derivative (cis-DMAAM) that can undergo a cis-trans photoisomerization reaction in both solution and in its crystal form was chosen as the photomechanical active element. Both the cis and trans isomerization reactions lead to an amorphous mixture that has very different properties than the single component reactant. Nanowires, with a diameter less than 200 nm, made from the cis or trans-DMAAM spontaneously coil to a dot when pulsed with visible 475 nm light. See Kim, T.; Al-Muhanna, M. K.; Al-Suwaidan, S. D.; Al-Kaysi, R. O.; Bardeen, C. J. Photoinduced Curling of Organic Molecular Crystal Nanowires. Angew. Chemie Int. Ed. 2013, 52, 6889-6893, doi:10.1002/anie.201302323—incorporated herein by reference in its entirety.
In view of the foregoing, one objective of the present invention is to provide a method of harnessing a type of photomechanical response based on a different crystal morphology of an anthracene derivative. As described herein, crystal growth conditions are tuned to control the faceting in molecular crystals composed of the anthracene derivative. This leads to block-like or tetragonal microcrystals that undergo spontaneous delamination (peeling) after a brief pulse of 220-420 nm light. This process can be repeated multiple times on the same t-block, uniformly peeling off a layer with every pulse of light. In addition to demonstrating a novel photomechanical effect made possible by control of crystal shape and faceting, the repetitive photoinduced delamination may also be used in novel materials with photo-renewable surfaces, or for various other applications.